Rice Genomics and Genetics 2024, Vol.15, No.2, 69-79 http://cropscipublisher.com/index.php/rgg 71 the function and expression patterns of disease resistance genes, more disease-resistant rice varieties can be developed. This will not only help reduce the threat of diseases to global rice production, but also help reduce dependence on pesticides and reduce agricultural production costs. 2.2 Diversity and mutation mechanism of rice blast fungus Rice blast is an important pathogenic fungus of rice, and its diversity and mutation mechanism pose a serious threat to rice production. When researching this area, we need to gain a deeper understanding of the diversity of pathogens and how they mutate in different environments. The diversity of M. oryzae is mainly reflected in the genetic differences between different strains. These differences can lead to different abilities of different pathogen strains to resist straw rice, thus affecting the yield and quality of rice. For example, a strain of rice blast fungus discovered in Guangdong Province, China, has a relatively strong ability to fight rice. By analyzing the genome of this strain, scientists discovered a series of genes that are highly adapted to it, allowing it to infect rice plants more efficiently. This example highlights the real-world impact of M. oryzae diversity, as the emergence of this strain could lead to a threat to traditional rice varieties, requiring more resistant varieties to maintain agricultural production. The diversity of pathogenic fungi is also reflected in the variability of their life cycles. The rice blast fungus may adopt different life cycle strategies in different environments, which results in certain variability in its disease prevalence in different regions or seasons. For example, during dry seasons, M. oryzae may adopt a dormant life cycle to adapt to the dry conditions of the environment. And during the wet season, it may transform into a more invasive life cycle to infect rice plants more effectively (Nasruddin and Amin, 2013). In terms of mutation mechanism, the genome of M. oryzae has certain variability, which provides a genetic basis for its adaptation to different environmental conditions. Genome variation can be achieved through a variety of ways, including genetic recombination, gene mutation, etc. For example, in some cases, genetic recombination may occur between two different strains of M. oryzae, resulting in subsequent strains with new genetic characteristics that make them better suited to specific environments. This mechanism of genome variation enables pathogenic fungi to adapt to different ecological conditions in a relatively short period of time, posing challenges to agricultural production. Another mechanism of variation is genetic mutation, where the gene itself changes randomly. This variation may cause the pathogen to exhibit new characteristics, sometimes new adaptations against resistant varieties. For example, some studies have found that certain strains of the rice blast fungus have acquired the ability to infect certain resistant varieties through genetic mutations. This mutation mechanism allows pathogenic fungi to quickly adapt to new resistant varieties in farmland, exacerbating the spread and damage of the disease (Chakraborty et al., 2021). 2.3 Molecular markers and mapping of rice blast resistance genes Molecular markers and mapping of rice blast resistance genes are important means to improve rice disease resistance and cultivate disease-resistant varieties. By in-depth studying the distribution, genetic mechanism and diversity of resistance genes, scientists have provided more possibilities for future rice breeding work. Rice blast caused by Magnaporthe oryzae is one of the most important fungal diseases of rice. The use of disease resistance genes to prevent and control this disease is the most economical, effective and environmentally friendly method. For example, in a study by the Academy of Agricultural Sciences, a new gene Pijx related to rice blast resistance was identified on chromosome 12 of rice. This gene has broad-spectrum resistance throughout the growth period; the Pijx protein interacts with the ATP synthase β subunit It interacts with the base and promotes its ubiquitination and degradation, thereby activating the activity of respiratory burst oxidase, inducing a burst of activated oxygen, and making the rice strain acquire resistance (Xiao et al., 2023) (Figure 1).
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